Overview: The importance of glycosylation in the biology of lympho-hematopoietic development and function is well established. In human, several disorders of hemostasis have been associated with abnormal oligosaccharide processing (1-8). Most secretory proteins (coagulation factors, hormones, enzymes, and antibodies) are glycoproteins. Previous studies have shown that glycosylation plays an important role in their biological function and in turnover, which in turn may play a role in governing the metabolic state of an individual. In recent years, genetically altered mouse strains that lack specific glycosyltransferases have been found to exhibit significant abnormalities in their hematopoietic, hemostatic and metabolic functions (9-14). Some of these abnormalities have been subtle and would have been missed in absence of standardized panels of screening tests designed to detect these abnormalities as well as assays developed to further evaluate possible specific defects. The functions of the Hematology/Coagulation Core are to perform screening assays to identify phenotypic abnormalities in hematopoiesis, hemostasis, and metabolic functions of the genetically altered mouse strains to be generated by the four projects of this Program Project Grant (PPG). Results of the studies by this core will be recorded, analyzed, interpreted and made available to the corresponding project leaders in a form that is readily accessed and compared, such as Excel spreadsheets and common graphic files. The phenotypic results obtained will help indicate specific cell types affected and possible future experiments by the projects in further addressing the specific aims of this PPG.